Fine Structure in Photoluminescence Spectrum of S2 Center in Sodalite
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Phys Chem Minerals (2007) 34:477–484 DOI 10.1007/s00269-007-0161-y ORIGINAL PAPER – Fine structure in photoluminescence spectrum of S2 center in sodalite Aierken Sidike Æ Alifu Sawuti Æ Xiang-Ming Wang Æ Heng-Jiang Zhu Æ S. Kobayashi Æ I. Kusachi Æ N. Yamashita Received: 18 December 2006 / Accepted: 6 April 2007 / Published online: 12 June 2007 Ó Springer-Verlag 2007 Abstract The photoluminescence and excitation spectra stretching vibration of the isotopic species of 32S34S–,a 32 – of sodalites from Greenland, Canada and Xinjiang (China) main peak due to that of the isotopic species of S2 and are observed at 300 and 10 K in detail. The features of the five peaks due to phonon sidebands of the main peak. emission and excitation spectra of the orange-yellow flu- – orescence of these sodalites are independent of the locality. Keywords Sodalite Á Photoluminescence Á S2 center Á The emission spectra at 300 and 10 K consist of a broad Heat treatment Á Fine structure band with a series of peaks and a maximum peak at 648 and 645.9 nm, respectively. The excitation spectra ob- tained by monitoring the orange-yellow fluorescence at 300 Introduction and 10 K consist of a main band with a peak at 392 nm. The luminescence efficiency of the heat-treated sodalite Natural sodalite represented by the ideal formula Na8Al6 from Xinjiang is about seven times as high as that of un- Si6O24Cl2 or 3(Na2OÁAl2O3Á2SiO2)Á2NaCl is a well-known – treated natural sodalite. The emission spectrum of the S2 fluorescent mineral emitting orange-yellow fluorescence center in sodalite at 10 K consists of a band with a clearly under ultraviolet (UV) light. Results of early investigations resolved structure with a series of maxima spaced about were reviewed by Kirk (1954, 1955). Kirk (1954) observed 560 cm–1 (20–25 nm) apart. Each narrow band at 10 K the emission and excitation spectra of the synthetic sodalite shows a fine structure consisting of a small peak due to the 3(Na2OÁAl2O3Á2SiO2)Á1.0NaClÁ0.25Na2SÁ0.25Na2SO4 at 293 and 77 K under 365 nm excitation. The emission spectra extended from about 500 to beyond 700 nm. The emission spectrum at 293 K showed a small amount of structure & A. Sidike Á A. Sawuti Á X.-M. Wang Á H.-J. Zhu ( ) with a most intense peak located at 658 nm, whereas School of Maths–Physics and Information Sciences, Xinjiang Normal University, Urumqi, Xinjiang 830054, China the emission spectrum at 77 K showed a clearly resolved e-mail: [email protected] structure with a series of maxima spaced about 20 nm apart with a most intense peak located beyond 700 nm. S. Kobayashi The excitation spectrum consisted of a structureless band Department of Applied Science, Faculty of Science, Okayama University of Science, Ridai-cho, with a peak at 400 nm (Kirk 1954). Kirk (1955) concluded Okayama 700-0005, Japan that the orange-yellow fluorescence is due to the presence of sodium polysulfide. Later, the orange-yellow fluorescence I. Kusachi – has been assigned to S2 molecule ions in sodalite. The Department of Earth Sciences, Faculty of Education, – – – Okayama University, Tsushima-naka, optical spectra of the O2 ,S2 and Se2 centers in natural Okayama 700-8530, Japan and synthetic sodalites have been reported by some researchers (Hodgson et al. 1967; Taylor et al. 1970; van N. Yamashita Doorn and Schipper 1971; Chang and Onton 1973; Department of Physics, Faculty of Education, Okayama University, Tsushima-naka, Tarashchan 1978; Schlaich et al. 2000; Gaft et al. 2005). Okayama 700-8530, Japan Taylor et al. (1970) observed the emission and excitation 123 478 Phys Chem Minerals (2007) 34:477–484 – – spectra of the S2 center in synthetic chloro-sodalite at substitute for Cl ion that is incorporated into the cage. The 110 K. The emission spectrum with the most intense peak at structure on the orange-yellow emission band of sodalite is about 670 nm consisted of a band structure with a separa- banded due to the symmetric vibration of the diatomic tion of 556 cm–1. The excitation spectrum obtained by sulfur molecules (Tarashchan 1978; Marfunin 1979; monitoring the emission at 600 nm consisted of a struc- Gorobets and Rogojine 2002). tureless band with a peak at about 394 nm (Taylor et al. The objectives of this investigation are (1) to observe 1970). Chang and Onton (1973) synthesized various types the luminescence spectra of natural sodalites from Green- of sodalite. The emission spectra of 3(Na2OÁAl2O3Á land, Canada and Xinjiang (China) in detail, (2) to study 2SiO2)Á2NaClÁNa2SO3 under 366 nm excitation consisted the effect of heat treatment on the luminescence efficiency of a band at 300 K with a small amount of structure whose of sodalite and (3) to determine fine structures on emission peak is located at 677 nm and a band at 78 K with a clearly bands at low temperatures. resolved structure whose most intense peak is located at about 680 nm (Chang and Onton 1973). Tarashchan (1978) – observed the emission spectra of the S2 centers in sulfur- Experimental containing aluminosilicate minerals, sodalite, hackmanite, vishnevite, hauyne, lazulite and scapolite. The emission In this investigation, four natural sodalites from Greenland, band of sodalite showed a small amount of structure with Canada and China (Xinjiang; #1 and #2) were analyzed. the most intense peak at about 708 nm. Schlaich et al. Two samples from Xinjiang were obtained from the col- (2000) obtained the absorption spectrum, which was trans- lections of the Xinjiang Geology and Mineral Museum. formed from the diffuse reflectance spectrum, and emission The crystal structures of the samples were examined – spectrum of Se2 in synthetic sodalite at room temperature. using an X-ray powder diffraction system (Rigaku RAD- The absorption spectrum consisted of three absorption bands 1B). The sodalite structure was ascertained by comparing with peaks at 20.00, 28.00 and 40.00 kcm–1. The emission the data with ICDD Card 37-476 for sodalite. spectrum, which was obtained under 28.00 kcm–1-band The chemical compositions of the natural sodalites were excitation at 364 nm (27.47 kcm–1)withanAr+-pumped dye determined by electron probe microanalysis (EPMA) laser, consisted of two bands located in red and blue regions. (JEOL, JXA-8900). Before the measurement by EPMA, the –1 Schlaich et al. (2000) attributedP the 20.00 andP 28.00 kcm surface of each test piece was polished flat and smooth. 2 2 3 – 3 – bands to the Õg fi Õu and g fi u transitions, The chemical composition in weight % was determined – respectively, within Se2 P, and red andP blue emission bands to from the mean of the data obtained at ten points of a test 2 2 3 – 3 – the Õu fi Õg and u fi g transitions, respec- piece. tively. Gaft et al. (2005)observedthelaser-inducedtime- In preparing sulfur-doped sodalite, grains of natural – resolved luminescence spectra of the S2 center in natural sodalite were sufficiently powdered using an agate mortar. sodalite at 300 and 77 K. A mixture of powder sodalite and sulfur (10–50 wt%) was The optical properties and paramagnetic resonance heated in a quartz crucible at 800–1,100°C for 30 min in – – – – spectra of O2 ,S2 , SeS and Se2 ions in various alkali– air. Powder sodalite without sulfur was also heated under halide crystals have been reported by some researchers the same conditions for comparison. After the heat treat- (Rolfe et al. 1961; Rolfe 1964;Kirketal.1965; Rolfe ment, the sample was rapidly quenched to room tempera- 1968; Ikezawa and Rolfe 1973; Rebane and Rebane 1974). ture by placing the crucible on a metal plate at room – The emission spectra of O2 ions in alkali–halides at low temperature and using an air blower. temperatures consist of a series of more than 12 narrow Before the measurement of luminescence spectra, grains bands at intervals of 900-1,100 cm–1 in the blue-green re- of fluorescent sodalite were sufficiently powdered using an gion to the red region (Rolfe et al. 1961; Rolfe 1964; agate mortar. The powdered sample was packed into a – Ikezawa and Rolfe 1973). In the emission spectra of S2 , sample holder with a synthetic quartz-glass cover. – – SeS and Se2 ions in alkali halides, the intervals of the The measuring system of photoluminescence (PL) and narrow bands are about 600–640, 460 and 300 cm–1, excitation spectra was almost the same as that used in respectively (Kirk et al. 1965; Rolfe 1968; Ikezawa and previous studies (Aierken et al. 2006a, b). In the mea- Rolfe 1973). surement of luminescence spectra, a 200 W deuterium – – The luminescence properties of the O2 and S2 centers lamp (Hamamatsu Photonics L1835), a 500 W xenon in minerals are reviewed by Tarashchan (1978), Marfunin short-arc lamp (Ushio UXL-500D) and a 50 W halogen (1979) and Gorobets and Rogojine (2002). The crystal tungsten lamp (Ushio JC12V-50W) were used as excitation structure of the sodalite family is built up from cubo- light sources. octahedral cages of AlO4 and SiO4 groups (Taylor et al. In the measurement of PL spectra, excitation wave- – 1970; Denks et al. 1976). Molecule ion S2 in sodalite can lengths with a bandwidth of 4 nm were selected using a 123 Phys Chem Minerals (2007) 34:477–484 479 Ritsu MC-50L grating monochromator. A band-pass glass Results filter or an interference filter was set in front of the sample to eliminate stray light from the excitation source. Obser- The chemical compositions of the natural sodalites exam- vation wavelengths with a bandwidth of 0.15-1 nm were ined by EPMA are shown in Table 1.